The present invention relates to a light emitting device, a method of manufacturing a light emitting device, and an image display device, particularly a solid state light emitting device such as a light emitting diode (hereinafter also referred to as “LED”).
There is a known light emitting device having a layered structure including a substrate and a semiconductor layer placed thereon. Light from a light emitting portion is transmitted through the substrate and emitted outside the light emitting device. The light emitting device produced simply by placing a substrate on a light emitting portion sometimes confines light as the light is totally reflected by the interfaces between the substrate and the air, between the light emitting portion and the substrate, and between other layers having different refractive indexes. It has also been known that such a light emitting device produced simply by placing a substrate on a light emitting portion supplies emitted light having a radiation distribution characteristic with a horizontally flat shape. For example, if it is requested that light be efficiently supplied toward an object for illumination as in the light source portion of an image display device, the light emitting device cannot efficiently supply light in a prescribed illumination direction. In order to improve the efficiency of how much emitted light is extracted to the outside (hereinafter as the “outcoupling efficiency”) in the light emitting device, and efficiently supply light in a prescribed illumination direction, the light emitting device is for example covered by a semispherical lens. A semispherical lens having a larger size than the light emitting device is employed, so that the total reflection can be reduced at the interface between the light emitting device and the air, while a virtual image having a larger area than that of the light emitting device forms. When for example a light emitting device and lenses are combined to supply light, as the area of the virtual image of the light emitting device increases, light that can be taken by the lenses decreases in some cases. JP-A-2004-128445 discloses a technique of improving the outcoupling efficiency and efficiently supplying light in a prescribed illumination direction without increasing the area of the virtual image.
JP-A-2004-128445 discloses a technique of providing an optical device having a wavelength of a very small order on the surface of a light emitting device. Such a very small optical device can be formed by reforming with laser light. However, a very small region must be irradiated with laser light, which makes it difficult to manufacture the device and pushes up the cost or the yield can be reduced because of necessary processing to the light emitting devices.